In modern television or radio broadcast stations, compressed digital data streams are typically used to carry video and/or audio data for transmission. For example, the Advanced Television Systems Committee (ATSC) standard for digital television (DTV) broadcasts in the United States adopted Moving Picture Experts Group (MPEG) standards (e.g., MPEG-1, MPEG-2, MPEG-3, MPEG-4, etc.) for carrying video content and Digital Audio Compression standards (e.g., AC-3, which is also known as Dolby Digital®) for carrying audio content (i.e., ATSC Standard: Digital Audio Compression (AC-3), Revision A, August 2001). The AC-3 compression standard is based on a perceptual digital audio coding technique that reduces the amount of data needed to reproduce the original audio signal while minimizing perceptible distortion. In particular, the AC-3 compression standard recognizes that the human ear is unable to perceive changes in spectral energy at particular spectral frequencies that are smaller than the masking energy at those spectral frequencies. The masking energy is a characteristic of an audio segment dependent on the tonality and noise-like characteristic of the audio segment. Different known psycho-acoustic models may be used to determine the masking energy at a particular spectral frequency. Further, the AC-3 compression standard provides a multi-channel digital audio format (e.g., 5.1 channels format) for digital television (DTV), high definition television (HDTV), digital versatile discs (DVDs), digital cable, and satellite transmissions that enables the broadcast of special sound effects (e.g., surround sound).
Existing television or radio broadcast stations employ watermarking techniques to embed watermarks within video and/or audio data streams compressed in accordance with compression standards such as the AC-3 compression standard and the MPEG Advanced Audio Coding (AAC) compression standard. Typically, watermarks are digital data that uniquely identify broadcasters and/or programs. Watermarks are typically extracted using a decoding operation at one or more reception sites (e.g., households or other media consumption sites) and, thus, may be used to assess the viewing behaviors of individual households and/or groups of households to produce ratings information.
However, many existing watermarking techniques are designed for use with analog broadcast systems. In particular, existing watermarking techniques convert analog program data to an uncompressed digital data stream, insert watermark data in the uncompressed digital data stream, and convert the watermarked data stream to an analog format prior to transmission. In the ongoing transition towards an all-digital broadcast environment in which compressed video and audio streams are transmitted by broadcast networks to local affiliates, watermark data may need to be embedded or inserted directly in a compressed digital data stream. Existing watermarking techniques may decompress the compressed digital data stream into time-domain samples, insert the watermark data into the time-domain samples, and recompress the watermarked time-domain samples into a watermarked compressed digital data stream. Such decompression/compression may cause degradation in the quality of the media content in the compressed digital data stream. Further, existing decompression/compression techniques require additional equipment and cause delay of the audio component of a broadcast in a manner that, in some cases, may be unacceptable. Moreover, the methods employed by local broadcasting affiliates to receive compressed digital data streams from their parent networks and to insert local content through sophisticated splicing equipment prevent conversion of a compressed digital data stream to a time-domain (uncompressed) signal prior to recompression of the digital data streams.